In my duotone of the woman on the stairs, I found that it helped the illusion if there was a shadow on the wall from her hand. On a separate layer I made a rough outline of her hand, placed that layer under her layer, filled it with black, making a box blur then lowered the opacity.
In the original photo, she was facing the other direction. I flipped her horizontally so that the lighting in the composite would be consistent.
I used a 2 pixel eraser at 28% to soften the wisps of her hair.